Reproduction of Cystopus Candidus , Liv. 335 
extent its original shape, although its apex appears in some 
sections to be disorganized (Fig. 18). In most cases a portion 
at least of the dense protoplasm which accompanied the male 
nucleus in its passage down the tube can be observed after 
the withdrawal of the latter. 
The fusion-nucleus in the oospore now begins to undergo 
changes. It increases in size ; the network becomes more 
visible and stains more deeply, and the dense mass of proto- 
plasm in its immediate neighbourhood begins to disappear, 
probably being used up to nourish the growing nucleus. The 
nucleolus then disappears, and the nuclear network divides up 
into chromosomes, which contract into an irregular spherical 
mass at the centre of the nucleus (Figs. 21, 22, 23), and 
presents the same appearance as occurs in the nuclei of the 
oogonium just previously to their division. The nucleus then 
divides, and although I have not been able to observe the 
details satisfactorily, it appears to follow the normal course 
of karyokinesis. The number of chromosomes present in the 
equatorial plate before division appears to be considerably in 
excess of the number observed in the nuclei of the oogonium, 
but it is very difficult to make sure. By counting as care- 
fully as possible twenty to twenty-four or even more appear 
to be present, and the impression is produced that the 
number is certainly much larger than that observed in the 
oogonium. 
Meanwhile the membrane around the oospore — the exo- 
spore — becomes distinctly visible as a moderately thick cell- 
wall. The columnar wall has appeared as minute projections 
on the inner layer (Figs. 21, 22), and further development of 
the wall accompanies the changes going on in the contents 
of the oospore, so that it is perfectly easy to follow the 
changes which take place in its further development in 
consecutive order, by using the formation of the wall as an 
index. 
The two nuclei of the oospore (Figs. 24, 25) now undergo 
changes similar to those described for the primary nucleus, 
and finally each one divides into two, so that we have now 
